1. Field of the Invention
The present invention relates to a phasing adder, an ultrasound probe, an acoustic sensor and an ultrasound diagnosis apparatus.
2. Description of Related Art
A conventional ultrasound diagnosis apparatus which performs internal inspection by emitting ultrasound waves in a subject, receiving reflected waves of the ultrasound waves and analyzing the received reflected waves is known. In such ultrasound diagnosis, a subject can be examined in a non-destructive and non-invasive manner. Therefore, such ultrasound diagnosis is widely used in various purposes such as medical examinations and internal inspection of architectures.
In such ultrasound diagnosis apparatus, the received ultrasound waves are converted into electric signals according to their intensity. Converters (transducers) such as piezoelectric devices are used to receive the ultrasound waves. With respect to each ultrasound wave, the mechanical deformation (expansion and contraction) of a piezoelectric element caused by the sound pressure of the ultrasound wave is converted into an electric signal (charge amount) according to the deformation level, and this electric signal is detected.
In recent ultrasound diagnosis apparatuses, the number of piezoelectric devices for receiving ultrasound waves is increased with the demand for high accuracy in images and the sampling rate of received date has also increased. In response, power consumption has increased in the ultrasound diagnosis apparatuses. In view of the above, JP 4557575 discloses a technique to decrease power consumption by reducing the number of FGAs (Floating Gate Amplifiers) used to amplify the signals.
With respect to LNAs (Low Noise Amplifiers) which are used to convert the deformation of piezoelectric devices into electric signals, conventionally, it has been difficult to improve the signal to noise ratio (SNR) while controlling power consumption since the supply current increases according to the cutback amount of noise.